Relationship between fractional anisotropy of cerebral white matter and metabolite concentrations measured using (1)H magnetic resonance spectroscopy in healthy adults.

Fractional anisotropy (FA) of water diffusion in cerebral white matter (WM), derived from diffusion tensor imaging (DTI), is a sensitive index of microscopic WM integrity. Physiological and metabolic factors that explain intersubject variability in FA values were evaluated in two cohorts of healthy adults of different age spans (N=65, range: 28-50years; and N=25, age=66.6±6.2, range: 57-80years). Single voxel magnetic resonance spectroscopy (MRS) was used to measure N-acetylaspartate (NAA), total choline-containing compounds, and total creatine, bilaterally in an associative WM tract: anterior corona radiata (ACR). FA values were calculated for the underlying, proximal and two distal WM regions. Two-stage regression analysis was used to calculate the proportion of variability in FA values explained by spectroscopy measurements, at the first stage, and subject's age, at the second stage. WM NAA concentration explained 23% and 66% of intersubject variability (p<0.001) in the FA of the underlying WM in the younger and older cohorts, respectively. WM NAA concentration also explained a significant proportion of variability in FA of the genu of corpus callosum (CC), a proximal WM tract where some of the fibers contained within the spectroscopic voxel decussate. NAA concentrations also explained a significant proportion of variability in the FA values in the splenium of CC, a distal WM tract that also carries associative fibers, in both cohorts. These results suggest that MRS measurements explained a significant proportion of variability in FA values in both proximal and distal WM tracts that carry similar fiber-types.

Corticotropin-releasing hormone (CRH) regulates macromolecular permeability via mast cells in normal human colonic biopsies in vitro.

OBJECTIVE: Persistent stress and life events affect the course of ulcerative colitis and irritable bowel syndrome by largely unknown mechanisms. Corticotropin-releasing hormone (CRH) has been implicated as an important mediator of stress-induced abnormalities in intestinal mucosal function in animal models, but to date no studies in human colon have been reported. The aim was to examine the effects of CRH on mucosal barrier function in the human colon and to elucidate the mechanisms involved in CRH-induced hyper-permeability. DESIGN: Biopsies from 39 volunteers were assessed for macromolecular permeability (horseradish peroxidase (HRP), (51)Cr-EDTA), and electrophysiology after CRH challenge in Ussing chambers. The biopsies were examined by electron and confocal microscopy for HRP and CRH receptor localisation, respectively. Moreover, CRH receptor mRNA and protein expression were examined in the human mast cell line, HMC-1. RESULTS: Mucosal permeability to HRP was increased by CRH (2.8+/-0.5 pmol/cm(2)/h) compared to vehicle exposure (1.5+/-0.4 pmol/cm(2)/h), p = 0.032, whereas permeability to (51)Cr-EDTA and transmucosal electrical resistance were unchanged. The increased permeability to HRP was abolished by alpha-helical CRH (9-41) (1.3+/-0.6 pmol/cm(2)/h) and the mast cell stabilizer, lodoxamide (1.6+/-0.6 pmol/cm(2)/h). Electron microscopy showed transcellular passage of HRP through colonocytes. CRH receptor subtypes R1 and R2 were detected in the HMC-1 cell line and in lamina propria mast cells in human colon. CONCLUSIONS: Our results suggest that CRH mediates transcellular uptake of HRP in human colonic mucosa via CRH receptor subtypes R1 and R2 on subepithelial mast cells. CRH-induced macromolecular uptake in human colon mucosa may have implications for stress-related intestinal disorders.

Lactobacillus rhamnosus strain GG prevents enterohemorrhagic Escherichia coli O157:H7-induced changes in epithelial barrier function.

Enterohemorrhagic Escherichia coli (EHEC) O157:H7 intimately attaches to intestinal epithelial monolayers and produces attaching and effacing (A/E) lesions. In addition, EHEC infection causes disruptions of intercellular tight junctions, leading to clinical sequelae that include acute diarrhea, hemorrhagic colitis, and the hemolytic-uremic syndrome. Current therapy remains supportive since antibiotic therapy increases the risk of systemic complications. This study focused on the potential therapeutic effect of an alternative form of therapy, probiotic Lactobacillus rhamnosus strain GG, to attenuate EHEC-induced changes in paracellular permeability in polarized MDCK-I and T84 epithelial cell monolayers. Changes in epithelial cell morphology, electrical resistance, dextran permeability, and distribution and expression of claudin-1 and ZO-1 were assessed using phase-contrast, immunofluorescence, and transmission electron microscopy and macromolecular flux. This study demonstrated that pretreatment of polarized MDCK-I and T84 cells with the probiotic L. rhamnosus GG reduced morphological changes and diminished the number of A/E lesions induced in response to EHEC O157:H7 infection. With probiotic pretreatment there was corresponding attenuation of the EHEC-induced drop in electrical resistance and the increase in barrier permeability assays. In addition, L. rhamnosus GG protected epithelial monolayers against EHEC-induced redistribution of the claudin-1 and ZO-1 tight junction proteins. In contrast to the effects seen with the live probiotic, heat-inactivated L. rhamnosus GG had no effect on EHEC binding and A/E lesion formation or on disruption of the barrier function. Collectively, these findings provide in vitro evidence that treatment with the probiotic L. rhamnosus strain GG could prove to be an effective management treatment for preventing injury of the epithelial cell barrier induced by A/E bacterial enteropathogens.

Bacterial cell surface hydrophobicity properties in the mediation of in vitro adhesion by the rabbit enteric pathogen Escherichia coli strain RDEC-1.

The role of hydrophobicity in the attachment of enteropathogens to gastrointestinal mucosa is controversial. In vitro binding of Escherichia coli RDEC-1 to rabbit intestine is dependent on the expression of pili. We examined in vitro adherence of piliated RDEC-1 after altering either the hydrophobicity of the organisms, the hydrophobicity of the substrate for attachment, or the surface tension of the suspending liquid. Hydrophobicity of RDEC-1 was determined using four complementary methods. In each assay piliated RDEC-1 demonstrated relatively more hydrophobic properties compared with both organisms grown to suppress pilus expression and a mutant that cannot express mannose-resistant pili. When piliated RDEC-1 were pretreated with tetramethyl urea to disrupt hydrophobic bonds surface hydrophobicity decreased. Concurrently, bacterial adherence to rabbit ileal microvillus membranes, mucus and mucin was reduced. Binding of piliated organisms to hydrophobic surfaces was significantly higher compared to both nonpiliated bacteria and the adherence of piliated RDEC-1 to relatively hydrophilic surfaces. Addition of propanol reduced the surface tension of the suspending liquid, and decreased adhesion of piliated RDEC-1 to polystyrene by 80%. Conversely, adherence of piliated organisms to a hydrophilic surface increased 12-fold after lowering the surface tension of the suspending liquid. We conclude that hydrophobic properties have a role in mediating in vitro adherence of this E. coli enteric pathogen.

Meta-analysis: Helicobacter pylori eradication treatment efficacy in children.

BACKGROUND: Several meta-analyses assessing the efficacy of anti-Helicobacter pylori treatment in adults have been published but a comparable meta-analysis in children is lacking. AIMS: To summarize the efficacy of treatments aimed at eradicating H. pylori in children and to identify sources of variation in treatment efficacy across studies. METHODS: We searched Medline, reference lists from published study reports, and conference proceedings for anti-H. pylori treatment trials in children. Weighted meta-regression models were used to find sources of variation in efficacy. RESULTS: Eighty studies (127 treatment arms) with 4436 children were included. Overall, methodological quality of these studies was poor with small sample sizes and few randomized-controlled trials. The efficacy of therapies varied across treatment arms, treatment duration, method of post-treatment assessment and geographic location. Among the regimens tested, 2-6 weeks of nitroimidazole and amoxicillin, 1-2 weeks of clarithromycin, amoxicillin and a proton pump inhibitor, and 2 weeks of a macrolide, a nitroimidazole and a proton pump inhibitor or bismuth, amoxicillin and metronidazole were the most efficacious in developed countries. CONCLUSIONS: Before worldwide treatment recommendations are given for eradication of H. pylori, additional well-designed randomized placebo-controlled paediatric trials are needed, especially in developing countries where both drug resistance and disease burden is high.

Combined challenge of mice with Citrobacter rodentium and ionizing radiation promotes bacterial translocation.

PURPOSE: Both enteric infection and exposure to ionizing radiation are associated with increased intestinal permeability. However, the combined effect of irradiation and enteric infection has not been described. We combined infection of mice with the enteric pathogen, Citrobacter rodentium, with exposure to ionizing radiation and assessed the impact on colonic epithelial ion transport, permeability and bacterial translocation. MATERIALS AND METHODS: Mice were infected with C. rodentium and then received whole-body exposure to 5 Gray gamma-radiation 7 days later. Three days post-irradiation, mice were euthanized and colons removed. Control groups included sham-infected mice that were irradiated and mice that were infected, but not irradiated. RESULTS: Macroscopic damage score and colonic wall thickness were increased by C. rodentium infection, but these parameters were not exacerbated by irradiation. Infection caused an increase in myeloperoxidase activity that was reduced by irradiation. Irradiation reduced the secretory response to electrical field stimulation, forskolin and carbachol; these changes were not altered by infection with C. rodentium. None of the treatments caused an increase in permeability to 51Cr-ethylenediaminetetraacetic acid (EDTA). However, combined infection and irradiation synergistically increased bacterial translocation to mesenteric lymph nodes, liver, spleen and blood. CONCLUSIONS: Although the combination of irradiation and infection did not exacerbate the individual effects of these challenges on ion secretion and mucosal permeability to 51Cr-EDTA, it dramatically increased susceptibility to bacterial translocation and bacteremia. These results have important implications for patients who develop an enteric infection during the course of abdominopelvic radiotherapy.

Current controversies associated with Helicobacter pylori infection in the pediatric population.

Helicobacter pylori is a human bacterial gastric pathogen, fulfilling each of Koch's postulates for causal inference for ulceration in children and adults. In addition many reports purport to show that the organism causes a variety of extra-intestinal manifestations in children. This review of the English language literature provides evidence that H. pylori is likely a cause of unexplained iron deficiency (sideropenic) anemia in children, even in the absence of gastrointestinal bleeding. Much stronger evidence is required however, before H. pylori infection can be considered as an etiologic agent in recurrent abdominal pain of childhood, unexplained short stature, protracted diarrhea in pre-schoolers and sudden infant death syndrome.

Benefit of ketotifen in patients with eosinophilic gastroenteritis.

PURPOSE: Eosinophilic gastroenteritis (EG) is a rare condition of unknown etiology characterized by vomiting, diarrhea, protein-losing enteropathy, and eosinophilic infiltration of the gastrointestinal mucosa. The potential association of EG with allergy and related mast-cell release of mediators led us to evaluate the ability of an antihistamine drug to modify the course of the disease. PATIENTS AND METHODS: Six patients with protracted gastrointestinal symptoms were diagnosed with EG because of histologic evidence of predominantly eosinophilic infiltrates in the gastrointestinal mucosa. Each patient was treated in an open trial for 12 months with ketotifen (Zaditen), an antihistamine of the H1 class that is known to stabilize mast cells. RESULTS: All six patients improved clinically; four also gained weight. Total serum IgE levels decreased after 4 to 6 months of therapy. Clearing of eosinophilic infiltrates was documented in the four patients who underwent follow-up mucosal biopsies. CONCLUSION: We conclude that ketotifen treatment represents a safe and effective alternative to traditional systemic corticosteroid therapy for treatment of EG.

Peptic ulcer disease in children: etiology, clinical findings, and clinical course.

The records of all children with peptic ulcer disease at the Hospital for Sick Children were retrospectively evaluated, excluding neonates, throughout a 5-year period. Only cases with a definite ulcer crater identified either at endoscopy or at surgery were included. There were 36 patients, 20 boys and 16 girls. Duodenal ulcers were more common than gastric ulcers (2.8:1). Ages ranged from 3 months to 17 years, with a mean age of 10 years. Patients were reviewed with respect to etiology of peptic ulcer disease, age when first examined, initial symptoms, and clinical course. Patients were divided into two groups, those with primary (n = 19) and those with secondary (n = 17) peptic ulcer disease. All peptic ulcers in patients younger than 10 years of age were secondary in nature. Secondary ulcers occurred generally in association with a severe underlying illness (11/17), and many ulcers necessitated emergency surgery because of perforation and/or severe hemorrhage (8/17). None of these patients had chronic or recurrent symptoms. In contrast, in children with primary peptic ulcer disease, initial symptoms were more benign. Most patients had abdominal pain and only one required emergency surgery. Children with primary duodenal ulcer disease had a high incidence of recurrent symptoms (67%), however, with surgery for intractable disease necessitated in 40%. Single-contrast barium meals were found to be unreliable in establishing a diagnosis of peptic ulcer disease, particularly cases of gastric ulcer disease.

Association of gastric metaplasia and duodenitis with Helicobacter pylori infection in children.

Helicobacter pylori infection causes chronic-active gastritis and is associated with peptic ulceration. However, the link between gastric H pylori colonization and duodenal ulcers is not well understood. Therefore, a retrospective, case-controlled study was conducted to determine whether H pylori infection is associated with gastric metaplasia and mucosal inflammation in the duodenum. Biopsy specimens from the duodenal bulb were obtained from 31 of 47 children with H pylori-induced gastritis. Two control groups, matched for age and sex, consisted of 33 children with normal antral histologic evaluation and 33 with H pylori-negative gastritis. Coded duodenal sections were stained with periodic acid-Schiff, hematoxylin-eosin, and silver to examine for gastric metaplasia, mucosal inflammation, and Helicobacter-like organisms, respectively. Thirteen of 31 (42%) H pylori-infected children had gastric metaplasia, in contrast to 1 of 33 with normal histologic characteristics (P < .0001) and 2 of 33 with H pylori-negative gastritis (P < .001). H pylori was detected overlying ectopic gastric mucosa in only 2 of 13 cases. Duodenal ulcers were identified endoscopically in 10 of 13 children with gastric metaplasia and 9 of 18 H pylori-infected subjects without metaplasia (P = NS). Twenty-four of 31 (77%) children with H pylori gastritis had duodenitis compared with 4 of 33 (12%) with H pylori-negative gastritis (P < .001) and 2 of 33 (6%) with a normal antrum (P < .001). Duodenitis was present in 14 of 19 children with H pylori infection and duodenal ulcers and 10 of 12 infected patients without mucosal ulceration (P not significant). These findings demonstrate a higher frequency of both gastric metaplasia and mucosal inflammation in the proximal small intestine of H pylori-infected children. However, there was a lack of correlation between the presence of duodenal ulceration and both gastric metaplasia and duodenitis.

Capsaicin as an inhibitor of the growth of the gastric pathogen Helicobacter pylori.

Capsaicin, the active ingredient in chili, has been implicated as both a cytoprotective and a detrimental agent to the gastric mucosa. The effect of capsaicin on Helicobacter pylori has not been investigated previously. Therefore, we performed in vitro time- and concentration-dependent studies to examine the growth of H. pylori in the presence of capsaicin. Capsaicin specifically inhibited growth of H. pylori dose-dependently at concentrations greater than 10 micrograms ml-1 (P < 0.05) but did not inhibit the growth of a human fecal commensal Escherichia coli strain. Bactericidal activity was observed within 4 h. Capsaicin continued to exhibit bactericidal activity when incubated at pH values as low as 5.4. Ingestion of chili, therefore, could have a protective effect against H. pylori-associated gastroduodenal disease. This effect deserves further study in animal models.

Pulsed-field gel electrophoresis indicates genotypic heterogeneity among Campylobacter upsaliensis strains.

To determine the genomic relatedness among a selection of animal and human Campylobacter upsaliensis isolates, macrorestriction profiles were generated for 20 C. upsaliensis strains, among 7 serogroups, using pulsed-field gel electrophoresis (PFGE). XhoI, SalI and SacII restriction enzyme profiles indicated genomic heterogeneity among strains. Using XhoI and SacII restriction enzyme digestion, genomic similarities between some pairs of strains were Lior serogroup specific. The genomic sizes of these isolates varied from 1.74 to 2.09 Mb. These results demonstrate molecular heterogeneity of this species similar to that found among Helicobacter pylori isolates. Among C. upsaliensis strains, PFGE is highly discriminatory and should prove a useful molecular typing method for epidemiological purposes.

Adherence of Vero cytotoxin-producing Escherichia coli of serotype O157:H7 to human epithelial cells in tissue culture: role of outer membranes as bacterial adhesins.

Escherichia coli of serotype O157:H7 are Vero cytotoxin-producing enteric pathogens that have recently been associated with outbreaks of haemorrhagic colitis, sporadic cases of haemorrhagic colitis and with the haemolytic uraemic syndrome. The organisms demonstrate attaching and effacing binding to the caecum and colon of orally infected gnotobiotic piglets, chickens and infant rabbits. E. coli O157:H7 cells adhere to the surface but do not invade the cytoplasm of human epithelial cell lines in tissue culture. Since outer membranes, lipopolysaccharides and flagella have been identified as bacterial adhesins on other enteric pathogens, we evaluated their roles in the binding of non-fimbriated E. coli O157:H7 to HEp-2 cells. Hyperimmune rabbit antisera were prepared to whole cells, outer membranes and flagella of E. coli O157:H7. The presence of antibody to homologous antigen was confirmed by dot blot immunoassays. Both antisera and purified outer membrane and flagellar antigens were co-incubated with bacteria and HEp-2 cells to quantitate inhibition of bacterial attachment. Adherence of E. coli O157:H7 to tissue culture cells was inhibited by rabbit antisera raised to whole cells (76.0 +/- 5.6% inhibition compared with bacterial adherence in the presence of pre-immune rabbit serum) and outer membranes (69.2 +/- 3.4% inhibition). In contrast, inhibition of bacterial attachment to tissue-culture cells was significantly less when two antisera to H7 flagella were co-incubated with E. coli O157:H7 and HEp-2 cells (12.4 +/- 7.6%; 6.0 +/- 3.5% inhibition). Outer-membrane extracts inhibited adherence to E. coli O157:H7 to HEp-2 cells in a concentration dependent manner whereas isolated flagella and lipopolysaccharide antigens did not inhibit bacterial attachment.(ABSTRACT TRUNCATED AT 250 WORDS)

Infectious gastroenterocolitides in children: an update on emerging pathogens.

The recognition that bacterial infections induce signal transduction responses in infected epithelial cells also provides new avenues to consider as novel forms of therapy. For example, the chemokine interleukin-8, which attracts neutrophils to sites of mucosal infection, is produced by epithelial cells of gastric and intestinal origin in response to bacterial infection. Inhibitors of chemokine production or inhibition of the biologic effects of neutrophil chemoattractants have the potential to reduce both mucosal inflammatory responses and the attendant clinical sequelae. Eukaryotic cells also respond to infection with elevations in cytosolic second messengers, including inositol triphosphate (IP3) and calcium ([Ca2+]i). In intestinal epithelium, these second messengers can mediate the diarrheal response to infection. Calcium/calmodulin inhibitors may have a beneficial effect in treating those gastrointestinal infections mediated through changes in the level of cytosolic free calcium. DuPont and colleagues showed, for example, that oral therapy with zaldaride maleate relieves symptoms of disease and shortens the duration of diarrhea in travelers with ETEC-induced diarrhea. Evaluation of additional signal transduction responses to microbial infections should provide both new insights into the pathogenesis of gastrointestinal infectious diseases and novel approaches to consider for the prevention and therapy for these human illnesses.

Helicobacter pylori-epithelial cell interactions: from adhesion to apoptosis.

Studies suggest that host cell signal transduction cascades are manipulated during infection with microbes, including the gastric pathogen Helicobacter pylori. Several putative adhesins have been proposed to mediate the attachment of H pylori to gastric epithelial cells. Following bacterial binding, a series of signalling pathways are activated in the infected gastric epithelial cell. These signals include both cytoplasmic (such as vacuolization, tyrosine phosphorylation and elevation of cytosolic calcium) and nuclear (proliferation, apoptosis and chemokine transcription) events. Research aimed at elucidating the interactions that occur between the host cell and the bacterium during infection should improve the limited knowledge of disease pathogenesis.

Understanding disease outcome following acquisition of Helicobacter pylori infection during childhood.

Helicobacter pylori causes chronic active (type B) gastritis in the overwhelming majority of infected individuals. The relative contribution of virulence factors in the bacterium and host responses to the microbial infection in determining which subjects will go on to develop complications - such as peptic ulceration, gastric cancers and gastric lymphomas - is the subject of current investigative activities.

Determinants of disease outcome following Helicobacter pylori infection in children.

Helicobacter pylori infection is primarily acquired during childhood, causes chronic, active gastritis and peptic ulcer disease, and is associated with the development of gastric malignancies. However, only a small number of infected individuals ever develop the more severe sequelae of peptic ulcer disease and gastric cancers. Therefore, the identification of bacterial and host factors that play a role in determining the outcomes and pathophysiology of infection is a major focus of current research. Recent advances in the understanding of disease pathogenesis are critically considered, with particular reference to the pediatric population.

Implications of antibiotic resistance in the management of Helicobacter pylori infection: Canadian Helicobacter Study Group.

Eradication of Helicobacter pylori from the gastric and duodenal mucosa is an important clinical goal in the treatment of infected patients with peptic ulcer disease and other H pylori-associated conditions. Although several oral drug combination regimens are associated with eradication rates of approximately 85% in controlled trials, the success rate in patients infected with a resistant strain of H pylori is closer to 75%. Resistance to metronidazole and clarithromycin, which are common components of combination treatment regimens, is of greatest concern. Reported rates of H pylori resistance to various antibiotics vary considerably. In Canada, the data documenting H pylori susceptibility are limited but suggest that resistance to these antibiotics varies geographically and within specific treatment groups. Although susceptibility testing is not a prerequisite for initial treatment of individual patients infected with H pylori, formal efforts to identify and monitor both the causes and prevalence of antibiotic resistance across Canada are a much needed step in the ongoing management of this important infection. Recommended treatment regimens may be useful, even for treating apparently resistant H pylori strains. However, it is important to understand the mechanisms of the development of resistant strains to manage patients with treatment failure better.

Turcot's syndrome: a diagnostic consideration in a child with primary adenocarcinoma of the colon.

We report the diagnosis of an adenocarcinoma of the colon in a 12-year-old girl in association with the presence of a small number of adenomatous polyps and a positive family history of a sibling with a central nervous system glioma. These findings implicate Turcot's syndrome as the cause for the development of intestinal and intracranial neoplasms in the two siblings. Since primary adenocarcinoma of the bowel is unusual in children, an underlying predisposing condition should be sought in affected cases.

Immune signalling responses in intestinal epithelial cells exposed to pathogenic Escherichia coli and lactic acid-producing probiotics.

Enterohaemorrhagic Escherichia coli O157:H7 and adherent-invasive Escherichia coli are two groups of enteric bacterial pathogens associated with haemorrhagic colitis and Crohn's Disease, respectively. Bacterial contact with host epithelial cells stimulates an immediate innate immune response designed to combat infection. In this study, immune responses of human epithelial cells to pathogens, either alone or in combination with probiotic bacteria were studied. Industrially prepared Lactobacillus helveticus strain R0052 was first examined by microarray analysis and then compared to broth-grown strains of R0052 and Lactobacillus rhamnosus strain GG using quantitative realt-time polymerase chain reaction. Results showed host immune activation responses increased following pathogen exposure, which were differentially ameliorated using probiotics depending on both the preparation of probiotics employed and conditions of exposure. These findings provide additional support for the concept that specific probiotic strains serve as a promising option for use in preventing the risk of enteric bacterial infections.